1. Field of the Invention
The present invention relates to a hold type image display unit as typified by a liquid crystal display unit, and more particularly, it relates to an image display unit which can reduce blurriness of a moving image.
2. Description of the Related Art
As an image display units, there are an impulse type display unit which intensively emits light in a moment that an image is written like a display unit using a cathode ray tube (CRT) and a hold type display unit which holds display from writing of an image to writing of an image of a next frame like an active matrix type display unit having a memory function per each pixel. As the active matrix type display unit, there is a liquid crystal display unit using a thin film transistor (TFT). In the liquid crystal display unit, an image written in a pixel by a TFT and a capacitor arranged in accordance with each pixel is held for a fixed time.
Since a response speed of the liquid crystal display unit is slow, the liquid crystal display unit has a problem that an after-image is generated when a moving image is displayed. As one of methods reducing this problem, there is a method using a filter which emphasizes a video signal in a time base direction (a time base emphasizing circuit).
A hold type display unit such as the liquid crystal display unit, however, cannot solve blurriness (which will be referred to as a moving image blur) of a moving image caused by an influence of a visual system integration owing to hold display itself even if a response speed of the liquid crystal is increased.
This problem and its countermeasure are described in “Fundamental Deterioration of Picture Quality for Moving Images Displayed on LCDs and Method for Improvement” by Taiichiro Kurita, Technical Report of IEICE EID2000-47 (2000-09), p. 13-18. It is to be noted that the moving image blur is generated in not only the liquid crystal display unit but also an organic electroluminescence display unit if this unit is of an active matrix type. The above-described reference describes a first method which shortens a hold time to approximate to display of the impulse type and a second method which doubles a 60-Hz frame frequency of an input video signal to 120 Hz by motion compensating means as countermeasures for the moving image blur.
The first method has a problem that means for shuts a backlight in synchronization with a video signal is required and display without flickering which is an advantage of the hold type display is deteriorated (a first problem). The second method has a problem that a sampling frequency of a video signal and a writing speed of a liquid must be respectively doubled and this operation imposes a great burden on a circuit scale or an operating speed of a circuit, thus involving a practical difficulty (a second problem).